Functional Muscle Function: Beyond Structural Anatomy

By: Dr. David Tiberio, Gray Institute

Learning the anatomy of all the muscles is a great challenge. I remember the anxiety of being tested on this knowledge and the pride of meeting the challenge.  What I did not appreciate at the time was how limited that knowledge was in providing insight into what muscles actually did during functional movements.  Knowledge of anatomy is necessary, but not sufficient to understand the role of muscles during human movements.

At the Gray Institute, we are constantly searching for the TRUTHS of human movement.  That search often forces us to reconsider what we have been taught, and as a result recognize that what we have done with our clients in the past may have been less that optimal.  What follows below are a few of the factors about muscle function that alter how we “practice” our professions.

Functional Muscle Function is ECONCENTRIC – Traditional teaching suggests that there are 3 types of muscle contractions: concentric (shortening), eccentric (lengthening), and isometric (no length change).  However, when we study the Chain Reaction Biomechanics of a common activity such as walking, it becomes clear that a muscle may be simultaneously lengthening (in one plane or at one joint), while shortening (in another plane or at another joint), and possibly experiencing no change in length (in another plane of joint).  At the Gray Institute the word for this “truth” of muscle function is ECONCENTRIC.

Functional Muscle Function is SYNERGISTIC – Structural anatomy encourages the concepts of muscles being agonists and antagonists: suggesting that one muscle opposes another.  In very isolated single-joint, single-plane motions this can be true.  In most functional movements, the agonist and antagonist perspective is completely false.  A synergy is a coordinated pattern of muscle activation.  These synergies are temporarily assembled (organized), and they are flexible (adjustable).  All coordinated movements involve synergies in which all the muscles are attempting to accomplish the same task (cooperating rather than competing).

Functional Muscle Function is TASK SPECIFIC – Because of our success at learning muscle anatomy, the tendency is to think of the function of any muscle as a constant: always the same.  However, since it is ECONCENTRIC and SYNERGISTIC, muscles can (and must) adjust to the movements required during a specific task, as well as the contributions of all the other muscles to that task.  Muscles must contribute differently to the task of swimming compared to the task of walking, or compared to the task of jumping.  The human machine is blessed with the ability to create different synergies for different tasks using the same muscles.  But, even the same task requires different synergies when the context changes.

Functional Muscle Function is CONTEXT DEPENDENT – Once the body is able to create a successful synergy to accomplish a task, it also needs to be able to adapt that synergy to different situations.  At the Gray Institute we say that even with a single task, the synergies that are created are dependent on the “context”.  The easiest way to think of the context is to consider the environment in which the task is taking place, the initial starting position of the body, and what other external forces are at work. The synergies must take advantage of gravity and ground reaction force.  Synergies must capture the momentum of movement.  Synergies must leverage the energy of elongated fascia and connective tissue.  These environmental forces are always changing.  One example of the effect of context on a task is walking. Walking on a smooth flat surface, walking on a uneven pitched surface, walking in a swimming pool, or walking on the moon each have a different environment (context) that requires adaptation in the synergy in order to successfully complete the task.

For more information on this topic as it pertains to specific muscles and function, be sure to check out our Functional Muscle Function channel as part of your Preferred subscription.

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